"Don Pearce" wrote in message
...
On Sun, 13 Jul 2003 16:45:01 +0100, "Keith G"
wrote:


OK, straight to the bottom (running out of time):



I didn't link the two. Rotating things causes problems, 'reading' things'
causes problems etc. Jitter has more to do with pits and lands. Pits and
lands have more to do with CDRs not being an 'exact' copy of the original
CD
(as SN will assert)....

Sorry, Keith but I had better lay this myth once and for all. Data
doesn't get stored on a CD that way. To make it robust bits are
distributed in a sort of pseudo-random fashion all over the place. The
decoder gathers therm up from wherever it finds them and assembles
them into a word which then gets presented to the DAC. The only place
jitter can occur is the final reading of that word into the DAC
itself.

So the nature of pits and lands on a CDR has absolutely no effect on
jitter in a digital system. They are either read properly, or they
aren't. If they are, then great - if not then either they can be
totally recreated through FEC, or the player will interpolate as best
it can. This would be a truly horrendous condition that will happen
only very rarely (once or twice in many discs).

Spinning things around, and systems that require high degrees of
mechanical accuracy are a bit of a pain though, and it would be nice
to see a time when the storage could be solid state. But that will
only happen when the price of 700MB is comparable to that of a CD
blank (about tuppence). I'm not holding my breath. But of course all
these problems go in trumps for a vinyl system (or we would have the
vinyl Walkman by now :-).

ps - I have no intention of entering the "Great Debate", just thought
you needed setting straight on the jitter thing.


Fair enough, Don. Coming from you I'm more inclined to say 'fine, I'm way
offbeam here' then. I have no real interest and am only quoting what odd
bits have come my way. See http://www.eyecote.com/qc/jitter.htm and
oft-reported jitter figures in the comix for example.

There really is no 'Great Debate' for me either - I love vinyl and greatly
prefer it to any other form of audio playback. I'm just killing time until
the vinyl group opens for biz....

:-)